the medial nasal prominences fuse to form the nasal septum, the philtrum, and the primary palate

as the maxillary prominences grow towards the midline, the nasal prominences grow inferiorly and medially; the maxillary and lateral nasal prominences meet at the nasolarcrimal groove (which later degenerates)

the lateral nasal prominences grow faster than the medial and eventually grow over the nasal pit to form the nasal sac which becomes the nasal cavity

paranasal sinuses

develop from the pneumatization of the maxilla, frontal, ethmoid, and sphenoid bones during childhood and adolescence

these two prominences grow towards each other and fuse in the 12th week; the median process gives rise to the anterior aspect of the hard palate; the lateral prominences give rise to most of the hard and soft palates

cleft lip and palate

can occur on any of the lines of fusion during the formation of the face and of the palate; may be uni- or bi- lateral (1/2500 live births)

Development of the Eye and Ear

neuroectoderm diverticula of the diencephalon give rise to the optic cups which pinch off parts of the ectoderm (lens placodes, from the optic placodes); lens placodes

Þ lens, optic cups Þ retina

the hyaloid artery is a branch of the opthalmic a which runs inside the stalk of the optic cup to supply the lens placode; the branch to the lens degenerates, but the rest remains as the central a of the retina

 posterior process of the ramus that ends in the head of the mandible

condyle (head)

 posterior process of the ramus

coronoid process

 anterior process of the ramus

mental foramen

 on anterolateral part of body; transmits mental vessels and nerve

lacrimal

 small bone on medial border of orbital fossa

fossa: on anterior border; contains lacrimal sac

nasolacrimal canal

occipital

temporal

 contains external auditory meatus:

Bony Region

anterior nasal aperture (piriform)

 pear-shaped aperature formed by nasal bones and maxilla

nasion

 depression at the root of the nose; superior junction of the nasal bones with the frontal bone

teeth

 teeth

alveolar processes

 on the mandible and maxilla; house the sockets for the teeth

zygomatic arch

 processes from the zygomatic and temporal bones come together in the arch

coronal suture, sagittal suture, bregma, lambdoid suture, lambda

: covered previously

Joints

temporomandibular (TMJ)

 modified synovial hinge joint between condyle of mandible, articular tubercle, and mandibular fossa of the temporal bone; articular capsule is somewhat loose, and dislocations are usually anteriorly; actions of the joint are anterior sliding, and hingelike rotation

Muscles

Muscles of Facial Expression  all innervated by the facial nerve (VII); most originate in fascia or bone, insert on skin

frontalis

 muscle of the forehead

action

: elevates the eyebrows; wrinkles the forehead

buccinator

 attaches lat. to alveolar processes of maxilla and mandible, inserts among the fibers of the obicularis oris muscle

action

: aids mastication by pressing the cheeks against the molars

depressor anguli oris

 depresses the corners of the mouth

zygomaticus major

 origin at zygomatic bone; inserts at corner of mouth

action

: elevates corner of mouth i.e. when smiling

levator labii superioris

 runs from infraorbital margin to the upper lip

action

: everts upper lip

orbicularis oris

 sphincter of the mouth

action

: alters the shape of the lips, compresses them against the teeth, purses them when whistling, etc

Other Muscles

platysma

origin

: fascia over the pectoralis major and deltoid

insertion

: inferior border of mandible in skin of face

innervation

: cervical branch of facial

action

: tenses skin of neck; relieves pressure on veins

masseter

origin

: zyogomatic arch

insertion

: ramus and coronoid process of mandible

innervation

: mandibular nerve (branch of trigeminal)

action

: elevates and protrudes mandible; closes jaw

Miscellaneous Structures

parotid gland

 largest of the salivary glands; located inferior to the ear

parotid duct 

emerges from anterior end of duct and passes anteriorly over the masseter, turns at the anterior border of the masseter and plunges into the buccinator muscle

papilla

 where the duct opens; opposite the second maxillary molar

buccal fat pad

 lies in cheek between the buccinator and the superficial facial mm

labial glands

 multiple acinous glands between the mucosa of the lips and the opening on the inner lip